one of my front Absorber is broken.
Which one should i change to Tein or Mazdaspeed?

 

Does Tein even make stand alone shocks?

 

don't think so. there is a flex type which use in rx8 they are adjustable.

 

You shouldn't just change 1 shock, replace all 4 at once.

Tein does not make standalone shocks/struts only full coilover. I would just go with stock springs/konis SA(yellows) unless you have an unlimited budget.